[amsat-bb] KB5WIA Update - CM79+

David Palmer KB5WIA kb5wia at amsat.org
Fri Aug 5 09:52:59 PDT 2011

Hi Everyone,

Here's an update on the CM79/CM89/CN70/CN80 plans.

CM79 is not an easy grid to work from.  Aside from being physically
remote, and being a strenuous hike (800' climbing) from the nearest
road, the actual topography of the grid is difficult for radio
operations.  The actual grid corner is in the middle of a thick
manzanita and poison-oak forest, 70 feet down the western slope of a
steep ridge.  In other words, from anywhere you are in CM79, there's a
steep hillside blocking the radio path to the east!  The best location
is actually the convergence of the four grids at the northeast tip of
CM79, where it's close enough to the ridge top that a remote antenna
can be used to get the signal over the ridge.   The problem then
becomes how to have the station itself on the grid convergence (down
the hill) and still be able to get signals "out".   Following
discussion with (and approval from!) ARRL HQ, here's the plan for
operation from CM79:

Station Setup for Overhead and Westerly satellite passes:
Full station set up directly over grid square intersection.
Specifically, I'll use the standard setup that I have used before,
consisting of two Yaesu FT-817ND radios hanging from a photographic
tripod, with the 6.4Ah LiFeP04 battery right next to the tripod. The
antenna is an Elk antenna on top of the tripod. The area of the grid
intersection will be marked with a ground tarp, and will be determined
with better than 20' accuracy with WAAS-GPS. Photo and video will be
used to document the station, GPS receiver, and surroundings.

Station Setup for Easterly satellite passes:
Since the view to the east is blocked by a ridge, 70' uphill, for
easterly passes I will use the exact same station as above, except
that the Elk antenna will be relocated to a second photographic tripod
perched on the ridge. The Elk will be connected via 100 feet of
LMR-400 coax, and I will use a preamp at the antenna to help overcome
the signal loss on the 70cm downlink. As above, all station operation
will be from directly over the grid intersection, including tuning,
transceivers, and power source. The Elk can be re-aimed once or twice
through the satellite pass to more or less keep up with the sat as it

What this means:

1)  Lower signals.
Expect my signal to be weaker than it is during my normal portable
operations (ie Death Valley, etc).  Since overhead and westerly passes
will have tree cover, and the easterly passes will have to use the
100-foot coax, my uplink signal to the birds won't be as strong as it
has been.

2)  Fading on eastern passes.
Anyone who has operated portable knows a big advantage of handheld
ops, that helps overcome the reduced gain of the smaller antennas, is
that you can rotate the antenna to exactly match the current
polarization of the satellite.  By necessity, I'll lose this advantage
on easterly passes with the remote antenna, since there's no way I can
be both at the operating location (to hear the return signals) and the
antenna (to flip it back and forth).  So, expect my signal to fade in
and out as the polarity changes.

3)  Time lag to hear sat on my RX end.
Since I'll be using a 100' run of LMR400 to carry both the uplink AND
downlink signals for the eastern passes, this necessarily means that
the antenna-mounted preamp is going to switch off during transmit.
The SP432VDG takes about 1-2 seconds to come back "on-line" after I
unkey, so on V/U birds if you come back to me immediately I may not
hear you.  Rapid exchanges on eastern passes probably won't work for
this reason, I'll have to take it slow.

4)  I'll be going QRT mid-pass once or twice to re-aim the antenna.
The Elk antenna has a fairly wide beamwidth, but certianly not enough
to cover a whole pass.  On eastern passes, I'll have to leave my
operating position and hike up to the ridge to point the antenna, then
will have to get back down to the operating location.  I won't have to
do this on overhead or western passes.

5)  For specific birds:

AO-51 if active:  This one has good strong signals.  Should be OK for
both eastern passes with the remote antenna and western passes with
the normal configuration.  My 1-2 second time lag on RX might be
problematic if the sat is congested.

SO-50:  This one's pretty weak to begin with.  I'll be lucky if I can
hear anything even with the preamp on the remote antenna, so don't
expect too much on eastern passes. Hopefully will be OK on overhead or
western passes.

AO-27:  Probably the same as AO-51.

FO-29:  Normal for overhead and western passes.  For eastern passes,
my preamp will cut out during transmit with the remote antenna, so I'm
pretty sure I won't be able to find my uplink.  I'll therefore be
effectively running half-duplex.  If you hear my call, come back to me
slowly, so I can use your downlink to zero my tuning.

AO-07:  Normal for overhead and western passes.  I'll likely have a
very weak uplink on the eastern passes using the remote antenna to get
over the hilltop -- input power to the Elk will only be around 2
watts.  Listen carefully and have patience.

VO-52:  This one actually works pretty well with the remote antenna
setup!  Expect some fading, but this one should be okay.

My website has the most recent information, and you can check the SPOT
tracker on my QRZ page to see if I'm at the location or not.

Hope to work many of you on the trip!

73 de Dave KB5WIA

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